Removal Inspection; Troubleshooting-Oxygen (O2) Sensor - Kohler Command PRO EFI Series Service Manual

Removal Inspection

NOTE: Apply anti-seize compound only to threads. Anti-seize compound will aff ect sensor performance if it gets
into lower shield of sensor.
1. If sensor has heavy deposits on lower shield, engine, oil, or fuel may be source.
2. If heavy carbon deposits are observed, incorrect engine fuel control may be occurring.
3. With sensor at room temperature measure heater circuit resistance, purple wire (Pin A) and white wire (Pin B),
resistance should be 8.1-11.1 Ω.
4. If a damaged sensor is found, identify root cause, which may be elsewhere in application. Refer to
Troubleshooting-Oxygen (O2) Sensor table.
5. A special "dry to touch" anti-seize compound is applied to all new oxygen sensors at factory. If recommended
mounting thread sizes are used, this material provides excellent anti-seize capabilities and no additional anti-seize
is needed. If sensor is removed from engine and reinstalled, anti-seize compound should be reapplied. Use an
oxygen sensor safe type anti-seize compound. It should be applied according to directions on label. Torque
sensor to 50.1 N·m (37 ft. lb.).

Troubleshooting-Oxygen (O2) Sensor

Condition
Continuous low voltage output (less
than 400mV) observed with throttle
openings of 30-40% or more.
Fault codes P0131, P0171, or P0174
may set.
Continuous high voltage output
(600mV or more) observed with
throttle openings of 20% or less.
Fault codes P0172 or P0132 may set.
No activity from sensor.
Diagnostic software displays
1.015 Volts continuously.
Fault codes P0031 or P0032 may set.
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Possible Cause
Shorted sensor or sensor circuit.
Shorted lead wire.
Wiring shorted to ground.
Upstream or downstream exhaust
leaks observed.
Air leak at sensor.
Restricted fuel supply.
Misfi re
Sensor failure-stuck lean.
Silica poisoning.
Contaminated gasoline.
Wiring shorted to voltage.
Overly rich condition due to
unmetered fuel entering combustion
chamber.
Cold engine. Engine temperature
below 150°F (66°C) as displayed by
diagnostic software.
Sensor failure-stuck rich.
Heater circuit open or shorted.
Engine keyed ON with sensor
disconnected.
Historic codes.
Contaminated gasoline.
Broken wire.
Damaged sensor.
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EFI SYSTEM
Conclusion
Replace sensor or replace and
properly route wiring.
Repair all exhaust leaks and torque
sensor to 50.1 N·m (37 ft. lb.).
Resolve fuel supply issues from tank
to engine. Test fuel pressure. Perform
repairs necessary.
A misfi re causing incomplete
combustion will result in lean (low
voltage) values.
Replace sensor.
Replace sensor. Identify and resolve
root cause.
Purge fuel system and retest.
Replace damaged harness.
Test fuel pressure. Inspect fuel pump
vent and evaporative emissions
hoses for raw fuel fl ow.
Inspect engine oil for fuel
contamination; drain and refi ll if
suspect.
Perform repairs as necessary.
Normal operation, or engine operated
in an excessively cold environment.
Replace sensor.
Replace sensor.
Secure and/or confi rm sensor
connection and clear codes.
Purge fuel system and retest.
Replace sensor.
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